1 /* 2 * mm/mprotect.c 3 * 4 * (C) Copyright 1994 Linus Torvalds 5 * (C) Copyright 2002 Christoph Hellwig 6 * 7 * Address space accounting code <alan@redhat.com> 8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 9 */ 10 11 #include <linux/mm.h> 12 #include <linux/hugetlb.h> 13 #include <linux/slab.h> 14 #include <linux/shm.h> 15 #include <linux/mman.h> 16 #include <linux/fs.h> 17 #include <linux/highmem.h> 18 #include <linux/security.h> 19 #include <linux/mempolicy.h> 20 #include <linux/personality.h> 21 #include <linux/syscalls.h> 22 #include <linux/swap.h> 23 #include <linux/swapops.h> 24 #include <linux/mmu_notifier.h> 25 #include <asm/uaccess.h> 26 #include <asm/pgtable.h> 27 #include <asm/cacheflush.h> 28 #include <asm/tlbflush.h> 29 30 #ifndef pgprot_modify 31 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) 32 { 33 return newprot; 34 } 35 #endif 36 37 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, 38 unsigned long addr, unsigned long end, pgprot_t newprot, 39 int dirty_accountable) 40 { 41 pte_t *pte, oldpte; 42 spinlock_t *ptl; 43 44 pte = pte_offset_map_lock(mm, pmd, addr, &ptl); 45 arch_enter_lazy_mmu_mode(); 46 do { 47 oldpte = *pte; 48 if (pte_present(oldpte)) { 49 pte_t ptent; 50 51 ptent = ptep_modify_prot_start(mm, addr, pte); 52 ptent = pte_modify(ptent, newprot); 53 54 /* 55 * Avoid taking write faults for pages we know to be 56 * dirty. 57 */ 58 if (dirty_accountable && pte_dirty(ptent)) 59 ptent = pte_mkwrite(ptent); 60 61 ptep_modify_prot_commit(mm, addr, pte, ptent); 62 #ifdef CONFIG_MIGRATION 63 } else if (!pte_file(oldpte)) { 64 swp_entry_t entry = pte_to_swp_entry(oldpte); 65 66 if (is_write_migration_entry(entry)) { 67 /* 68 * A protection check is difficult so 69 * just be safe and disable write 70 */ 71 make_migration_entry_read(&entry); 72 set_pte_at(mm, addr, pte, 73 swp_entry_to_pte(entry)); 74 } 75 #endif 76 } 77 78 } while (pte++, addr += PAGE_SIZE, addr != end); 79 arch_leave_lazy_mmu_mode(); 80 pte_unmap_unlock(pte - 1, ptl); 81 } 82 83 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, 84 unsigned long addr, unsigned long end, pgprot_t newprot, 85 int dirty_accountable) 86 { 87 pmd_t *pmd; 88 unsigned long next; 89 90 pmd = pmd_offset(pud, addr); 91 do { 92 next = pmd_addr_end(addr, end); 93 if (pmd_none_or_clear_bad(pmd)) 94 continue; 95 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); 96 } while (pmd++, addr = next, addr != end); 97 } 98 99 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, 100 unsigned long addr, unsigned long end, pgprot_t newprot, 101 int dirty_accountable) 102 { 103 pud_t *pud; 104 unsigned long next; 105 106 pud = pud_offset(pgd, addr); 107 do { 108 next = pud_addr_end(addr, end); 109 if (pud_none_or_clear_bad(pud)) 110 continue; 111 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); 112 } while (pud++, addr = next, addr != end); 113 } 114 115 static void change_protection(struct vm_area_struct *vma, 116 unsigned long addr, unsigned long end, pgprot_t newprot, 117 int dirty_accountable) 118 { 119 struct mm_struct *mm = vma->vm_mm; 120 pgd_t *pgd; 121 unsigned long next; 122 unsigned long start = addr; 123 124 BUG_ON(addr >= end); 125 pgd = pgd_offset(mm, addr); 126 flush_cache_range(vma, addr, end); 127 do { 128 next = pgd_addr_end(addr, end); 129 if (pgd_none_or_clear_bad(pgd)) 130 continue; 131 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); 132 } while (pgd++, addr = next, addr != end); 133 flush_tlb_range(vma, start, end); 134 } 135 136 int 137 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 138 unsigned long start, unsigned long end, unsigned long newflags) 139 { 140 struct mm_struct *mm = vma->vm_mm; 141 unsigned long oldflags = vma->vm_flags; 142 long nrpages = (end - start) >> PAGE_SHIFT; 143 unsigned long charged = 0; 144 pgoff_t pgoff; 145 int error; 146 int dirty_accountable = 0; 147 148 if (newflags == oldflags) { 149 *pprev = vma; 150 return 0; 151 } 152 153 /* 154 * If we make a private mapping writable we increase our commit; 155 * but (without finer accounting) cannot reduce our commit if we 156 * make it unwritable again. 157 */ 158 if (newflags & VM_WRITE) { 159 if (!(oldflags & (VM_ACCOUNT|VM_WRITE| 160 VM_SHARED|VM_NORESERVE))) { 161 charged = nrpages; 162 if (security_vm_enough_memory(charged)) 163 return -ENOMEM; 164 newflags |= VM_ACCOUNT; 165 } 166 } 167 168 /* 169 * First try to merge with previous and/or next vma. 170 */ 171 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 172 *pprev = vma_merge(mm, *pprev, start, end, newflags, 173 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 174 if (*pprev) { 175 vma = *pprev; 176 goto success; 177 } 178 179 *pprev = vma; 180 181 if (start != vma->vm_start) { 182 error = split_vma(mm, vma, start, 1); 183 if (error) 184 goto fail; 185 } 186 187 if (end != vma->vm_end) { 188 error = split_vma(mm, vma, end, 0); 189 if (error) 190 goto fail; 191 } 192 193 success: 194 /* 195 * vm_flags and vm_page_prot are protected by the mmap_sem 196 * held in write mode. 197 */ 198 vma->vm_flags = newflags; 199 vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, 200 vm_get_page_prot(newflags)); 201 202 if (vma_wants_writenotify(vma)) { 203 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); 204 dirty_accountable = 1; 205 } 206 207 mmu_notifier_invalidate_range_start(mm, start, end); 208 if (is_vm_hugetlb_page(vma)) 209 hugetlb_change_protection(vma, start, end, vma->vm_page_prot); 210 else 211 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); 212 mmu_notifier_invalidate_range_end(mm, start, end); 213 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 214 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 215 return 0; 216 217 fail: 218 vm_unacct_memory(charged); 219 return error; 220 } 221 222 asmlinkage long 223 sys_mprotect(unsigned long start, size_t len, unsigned long prot) 224 { 225 unsigned long vm_flags, nstart, end, tmp, reqprot; 226 struct vm_area_struct *vma, *prev; 227 int error = -EINVAL; 228 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 229 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 230 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 231 return -EINVAL; 232 233 if (start & ~PAGE_MASK) 234 return -EINVAL; 235 if (!len) 236 return 0; 237 len = PAGE_ALIGN(len); 238 end = start + len; 239 if (end <= start) 240 return -ENOMEM; 241 if (!arch_validate_prot(prot)) 242 return -EINVAL; 243 244 reqprot = prot; 245 /* 246 * Does the application expect PROT_READ to imply PROT_EXEC: 247 */ 248 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 249 prot |= PROT_EXEC; 250 251 vm_flags = calc_vm_prot_bits(prot); 252 253 down_write(¤t->mm->mmap_sem); 254 255 vma = find_vma_prev(current->mm, start, &prev); 256 error = -ENOMEM; 257 if (!vma) 258 goto out; 259 if (unlikely(grows & PROT_GROWSDOWN)) { 260 if (vma->vm_start >= end) 261 goto out; 262 start = vma->vm_start; 263 error = -EINVAL; 264 if (!(vma->vm_flags & VM_GROWSDOWN)) 265 goto out; 266 } 267 else { 268 if (vma->vm_start > start) 269 goto out; 270 if (unlikely(grows & PROT_GROWSUP)) { 271 end = vma->vm_end; 272 error = -EINVAL; 273 if (!(vma->vm_flags & VM_GROWSUP)) 274 goto out; 275 } 276 } 277 if (start > vma->vm_start) 278 prev = vma; 279 280 for (nstart = start ; ; ) { 281 unsigned long newflags; 282 283 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 284 285 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 286 287 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 288 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 289 error = -EACCES; 290 goto out; 291 } 292 293 error = security_file_mprotect(vma, reqprot, prot); 294 if (error) 295 goto out; 296 297 tmp = vma->vm_end; 298 if (tmp > end) 299 tmp = end; 300 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 301 if (error) 302 goto out; 303 nstart = tmp; 304 305 if (nstart < prev->vm_end) 306 nstart = prev->vm_end; 307 if (nstart >= end) 308 goto out; 309 310 vma = prev->vm_next; 311 if (!vma || vma->vm_start != nstart) { 312 error = -ENOMEM; 313 goto out; 314 } 315 } 316 out: 317 up_write(¤t->mm->mmap_sem); 318 return error; 319 } 320